The problem arises because some software has - since ASCII days - interpreted the grave as an opening single quote (a character that does not appear in the ASCII sequence because using opening single quotes is an English, not a US, habit). So if the same text is copied to a piece of software that interprets the grave literally, you get this result.

I have found that LyX/LaTeX users can avoid this by exporting via HTML which converts all the grave accents in LaTeX to opening single quotes.